A screw anchor includes a body having a head end that extends to a tip end through an intermediate portion defining an axis of the screw anchor, and a plurality of threads extending along the intermediate portion. Each of the plurality of threads includes a head side surface having a first angle relative to an axis perpendicular to the axis of the screw, and a tip side surface having a second angle relative to the axis perpendicular to the axis of the screw. The first angle is between about 30° and about 40°, and the second angle is between about 15° and about 25°.